init jest

Author: piecyk

.babelrc

@@ -1,4 +1,15 @@
 {
-  "presets": ["@babel/preset-react", "@babel/typescript"],
+  "presets": [
+    [
+      "@babel/env",
+      {
+        "targets": {
+          "browsers": ["last 2 versions"]
+        }
+      }
+    ],
+    "@babel/typescript",
+    "@babel/preset-react"
+  ],
   "plugins": ["@babel/proposal-class-properties", "@babel/proposal-object-rest-spread"]
 }

.editorconfig

@@ -0,0 +1,9 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 2
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true

package.json

@@ -9,17 +9,21 @@
     "dev": "run-p dev:*",
     "dev:webpack": "webpack-dev-server --mode development --content-base ./site",
     "dev:ts": "tsc --watch --preserveWatchOutput",
-    "build": "yarn run clean && tsc && webpack --mode production"
+    "test": "jest",
+    "build": "yarn run clean && tsc && yarn run test && webpack --mode production"
   },
   "devDependencies": {
     "@babel/core": "^7.2.2",
     "@babel/plugin-proposal-class-properties": "^7.3.0",
     "@babel/plugin-proposal-object-rest-spread": "^7.3.1",
+    "@babel/preset-env": "^7.3.1",
     "@babel/preset-react": "^7.0.0",
     "@babel/preset-typescript": "^7.1.0",
+    "@types/jest": "^23.3.13",
     "@types/react": "^16.7.22",
     "@types/react-dom": "^16.0.11",
     "babel-loader": "^8.0.5",
+    "jest": "^24.0.0",
     "npm-run-all": "^4.1.5",
     "typescript": "^3.3.0-rc",
     "webpack": "5.0.0-alpha.9",

src/Foo.ts

@@ -0,0 +1 @@
+export const sum = (x: number, y: number) => x + y

src/Sum.ts

@@ -0,0 +1,5 @@
+import { sum } from '../Sum'
+
+test('adds 1 + 2 to equal 3', () => {
+  expect(sum(1, 2)).toBe(3)
+})

src/__test__/Sum.test.ts

@@ -1,7 +1,7 @@
 import React from 'react'
 import ReactDOM from 'react-dom'
 
-import { add } from 'Foo'
+import { sum } from 'Sum'
 import Example from 'lib/Example'
 
 enum Check {
@@ -11,7 +11,7 @@ enum Check {
 
 const Foo = () => (
   <div style={{ fontSize: 24 }}>
-    Hello: {Check.Bar} | {add(3, 2)}
+    Hello: {Check.Bar} | {sum(3, 2)}
     <Example initialCounter={2} />
   </div>
 )

src/index.tsx

@@ -7,6 +7,7 @@ interface Props {
 export default function Example({ initialCounter }: Props) {
   // Declare a new state variable, which we'll call "count"
   const [count, setCount] = useState(initialCounter)
+  console.log('render: ', count)
 
   return (
     <div>